In the area of opto-electronic packages, it is generally accepted that the most time consuming and costly component of the package is the alignment of the optical fiber, or waveguide, to the semiconductor emitter or receiver. The traditional approach to this alignment requires that the two parts be micromanipulated relative to each other while one is operating and the other is monitoring coupled light. Once the desired amount of coupled light is attained, the two parts must be affixed in place in such a way as to maintain this alignment for the life of the product. This process, commonly referred to as active alignment, can be slow and given to poor yields stemming from the micromanipulation and the need to permanently affix the two objects without causing any relative movement of the two with respect to each other.
To alleviate this problem, opto-electronic package designs have been suggested which incorporate passive alignment techniques. These designs do not require activation of the opto-electronic device. Generally, they rely on some mechanical features on the laser and the fiber as well as some intermediate piece for alignment. By putting the pieces together with some adhesion mechanism, alignment can be secured and maintained for the life of the component. Typical of this technology is the silicon optical bench design. In this design, the laser is aligned via solder or registration marks to an intermediate piece, a silicon part, which has mechanical features--"v-grooves" --which facilitate alignment of an optical fiber. The drawbacks to this design are the number of alignments in the assembly process and the cost of the intermediate component. Additionally, these designs can be difficult to use with surface emitting/receiving devices because of the need to redirect the light coupled through the system.
Other approaches have been suggested which do not incorporate a silicon intermediate structure. Swirhun et al. (U.S. Pat. No. 5,631,988) suggests that defined features in a surface emitting laser array could be used as an alignment means for a structure that holds embedded optical fibers. This third structure adds complexity and adds to the overall tolerance scheme for the alignment system.
In other prior art, attempts have been made to cope with the dilemma of adding intermediate parts and their associated costs and tolerances. Matsuda (U.S. Pat. No. 5,434,939) suggests a design that allows direct fiber coupling to a laser by way of a guiding hole feature in the backside of the actual laser substrate. The precision with which such guiding holes can be manufactured is not currently adequate for reliable coupling. Additionally, the process of making a hole in the actual laser substrate can weaken an already fragile material. Furthermore, this design is not appropriate when it is desired to have light emit from the top surface of the opto-electronic device, commonly called a top emitter in the vernacular of the industry. In contrast, a bottom emitter is a photonic device wherein the emitted light propagates through the substrate and out the bottom surface of the device.
What is needed is a photonic device that allows direct passive alignment and attachment of an optical signal carrying apparatus, such as an optical fiber for example, via robust guide features formed integrally on the surface of the photonic device. This photonic device would enable precise positioning of the fiber relative to the active region with the potential for sub-micron alignment accuracy without the addition of interfacial alignment components. Furthermore, it would be advantageous if the fabrication method for the above is compatible with standard semiconductor processing equipment.